5 - Distributed Transducers for Active Control of Vibration

Abstract

This chapter provides a brief discussion of the basic theory and issues regarding the implementation of distributed actuators and sensors commonly encountered in active vibration control systems. Electrodynamic shakers can be readily modelled as point force inputs and the response of structures to these types of forcing functions are outlined. The chapter focuses on the relatively new theory of distributed piezoelectric actuators and sensors. The analysis presented is limited to a static approach where inertial effects associated with the actuator itself are ignored. However, the static approach is shown to be satisfactory in many cases and more recent studies on advanced theories, which include material dynamic terms, actuator-structure coupling, impedance effects as well as the dynamics of the associated electrical circuitry, are reviewed. The chapter also provides information to actuators and sensors based on advanced new materials such as shape memory alloy. Piezoelectric materials are used as sensors to measure structural motion by directly attaching them to the structure. Most contemporary applications of piezoelectricity use polycrystalline ceramics instead of naturally occurring piezoelectric crystals. The relationship between the applied forces and resultant responses of piezoelectric material depend upon a number of parameters such as the piezoelectric properties of the material, its size and shape and the direction in which forces or electrical fields are applied relative to the material axis.